Study of microstructural evolution and mechanical performance of selective laser melting pure tungsten deposit for process parameter optimization

The influence of laser energy density on internal defects, microstructure, and mechanical properties of pure tungsten (W) deposits fabricated by selective laser melting (SLM) is investigated in a wide range of processing parameters. The results demonstrate that the relative density and surface quality of pure W deposits can be significantly improved through coordinated optimization of process parameters. The relative density and surface quality of W deposits initially are improved and then degraded as laser energy density increases, allowing the identification of a broad processing window for SLM of pure W. Because of the high thermal gradient and rapid cooling characteristics inherent to the SLM process, W deposits predominantly exhibit fine columnar grains oriented along the build direction in a relatively broad processing window. Cracks are distributed vertically and propagate along the grain boundaries. Moreover, all W deposits exhibit negligible variation in grain morphology, size, and grain boundary distribution, indicating stable and consistent microstructural characteristics. The pure W deposits also demonstrate significantly enhanced nano-hardness compared to conventionally cast W substrates, which is attributed to grain refinement strengthening. The nano-hardness distribution in the vertical plane remains relatively uniform, despite local fluctuations caused by residual stress and microcracks. Furthermore, all samples display excellent wear resistance over a broad processing window, with similar friction coefficients and wear profiles. The dominant wear mechanisms are identified as delamination and abrasive wear, with slight adhesive wear. These results collectively indicate that SLM pure W deposits have favorable and stable microstructural and mechanical properties across a wide range of processing parameters. • A broad and robust process window for fabricating high-quality pure W deposits was established via SLM. • SLM pure W deposits was characterized by similar phase constituents and microstructures in a wide process window. • SLM pure W deposits exhibited consistent hardness and wear resistance, indicating a excellent mechanical stability.